FR2976967A1 - TRACER FLUIDS WITH MEMORY EFFECT FOR THE STUDY OF A PETROLEUM FACILITY - Google Patents

Abstract

The field of this invention is that of the exploration and exploitation of oil deposits. More specifically, this invention relates to the development of nanoparticles and tracer fluids containing them, intended to be injected into a well, and collected by inversion of the fluid flow by the same well. The tracer fluids according to the invention have the advantage of producing a fluorescent signal with a memory effect, that is to say a signal modified according to the physicochemical conditions encountered in the medium traversed by the nanoparticles after injection into the subsoil. geological. The analysis of the fluorescent signals in the fluids collected after diffusion makes it possible to deduce information on the characteristics of the oil reservoir.

Description

TRACER FLUIDS WITH MEMORY EFFECT FOR THE STUDY OF A PETROLEUM FACILITY

The field of this invention is that of the exploration and exploitation of oil deposits. More specifically, this invention relates to the development of nanoparticles and tracer fluids containing them, intended to be injected into a well, and collected by inversion of the fluid flow by the same well.

The tracer fluids according to the invention have the advantage of producing a fluorescent signal with a memory effect, that is to say a signal modified according to the physicochemical conditions encountered in the medium traversed by the nanoparticles after injection into the subsoil. geological. The analysis of the fluorescent signals in the fluids collected after diffusion makes it possible to deduce information on the characteristics of the oil reservoir.

BACKGROUND TECHNOLOGY

It is well known in the prior art to use tracers to obtain information on a petroleum deposit or more generally on a resource of a geological subsoil, a hydrocarbon deposit, water, gas, oil or oil. Techniques using, for example, tracers with different partition coefficients have been described. The principle is based in particular on chromatography. One of the tracers interacts more specifically with certain fluids contained in the rock, for example, the oil, and its diffusion will be curbed in the presence of oil. By quantifying the diffusion delay with respect to a tracer which interacts little or nothing with its environment (stealth tracer), we deduce the amount of oil contained in the deposit.

These methods of analysis may be conducted from a single well ("Single Weil Tracer Test") or two wells, including an injection well and a production well.

With regard to the state of the art specific to such tracers for injection water (tracer fluid) making it possible to probe oil deposits by diffusion between an injection well and a production well, mention may be made of US Patents 4,231,426 -B1 and 4,299,709-B1 which disclose aqueous tracer fluids comprising from 0.01 to 10% by weight of a nitrate salt associated with a bactericidal agent.

US Pat. No. 3,623,842 describes a method for measuring an oil saturation in the vicinity of a well ("Single Weil Tracer Test") of injecting a first partitioning tracer (water / oil), the latter releasing a tracer. stealth after a certain time of diffusion in the porous medium.

The Institute for Energy Technology (IFE) website puts on-line a power point presentation entitled SIP 2007 - 2009 "New functional traceus based on nanotechnology and radiotracer generators Department for Reservoir and Exploration Technology" (last modification dated March 7th, 2011 ). In particular, this paper suggests the use of surface-modified nanoparticles as a tracer for flow control in oilfields and oil wells and in process studies. More precisely, this presentation also describes functionalized tracers capable of emitting a modulated signal depending on the physicochemical conditions traversed.

In a completely different field, the French patent application FR2867180-A1 describes hybrid nanoparticles comprising, on the one hand, a core consisting of a rare earth oxide, optionally doped with a rare earth or an actinide or a mixture of grounds. rare or a mixture of rare earths and actinide and, secondly, a coating around this core, said coating consisting mainly of polysiloxane functionalized with at least one biological ligand covalently bonded. The core may be Tb3 + doped Gd2O3 based or uranium and the polysiloxane coating may be obtained by reacting an aminopropyltriethoxysilane, a tetraethylsilicate and triethylamine.

These nanoparticles are used as probes for the detection, monitoring, and quantification of biological systems.

We also know about ten families of molecules adapted and currently validated as a tracer for injection water in oil fields. These families of molecules are, for example, fluorinated benzoic acids or naphthalenesulphonic acids.

It is also known that fluorescent objects often have a fluorescence closely related to the physicochemical conditions encountered with a very strong possible variation of their emission spectra, their excitation spectra, their emission lifetime or their quantum yields.

For example, some compounds have a strongly temperature dependent emission or emission lifetime (fluorescence decline time) and are thus used in delocalized temperature measurement (J. Lakowicz, "Principles of fluorescence spectroscopy"). Springer 2006, page 216).

Other compounds such as fluorescein and its derivatives are in turn very sensitive to pH conditions and may have an emission intensity that varies by several orders of magnitude between an acidic and basic pH (N. Clonis, WH Sawyer, " Spectral properties of the prototropic forms of fluorescein in acqueous solution ", J. Fluorescence, 1996, 6, 147).

These variations may be irreversible or reversible depending on the compounds. If the use of fluorescent compounds as a tracer is known, the use of "irreversible" fluorescence modification is generally considered a disadvantage for the interpretation of tracing curves and quantifications.

However, the degradation of the fluorescence signal can nevertheless give information on the medium encountered and could then be used as a "memory effect" signal of the conditions encountered.

In the biological field, some fluorescence modification assays related to memory effects have been proposed: they are related to the meeting of a biomolecule 20 or a specific cell. For example, patent application US2010 / 0272651, it is suggested to use fluorescent tracers in connection with indicators for the determination of specific pharmacokinetics or biodistributions within organisms.

Nevertheless, to date, the use of "memory effect" signals in the petroleum field has never been described or even suggested.

In fact, the inventors have had to develop new tracers having a detectable time-resolved fluorescence (particularly related to lanthanide emission), even in the presence of a strong background related to the organic compounds present in the molecule. the different oils.

TECHNICAL PROBLEM AND OBJECTIVES TO BE REACHED

In this context, the present invention aims to satisfy at least one of the following objectives: to propose a new method for studying a solid medium, for example a petroleum deposit, by diffusion of a liquid through said medium solid, which is simple to implement and economical; to overcome the drawbacks of tracers for injection water from petroleum deposits according to the prior art; providing nanoparticles having a memory effect fluorescence signal, that is to say whose emission and / or excitation spectrum is modified as a function of the physicochemical conditions of the medium traversed; provide a new tracer fluid comprising these nanoparticles that can be used in particular in a method for studying a solid medium, for example a petroleum deposit by diffusion of said liquid through said solid medium and recovery by the same well by inversion of the flow.

BRIEF DESCRIPTION OF THE INVENTION These objectives, among others, are achieved by the invention, which concerns in the first place a method of studying a geological subsoil, such as a petroleum deposit, by diffusion of a injection liquid in said subsoil, characterized in that it comprises the following steps: injecting, in the subsoil to be studied, an injection liquid comprising nanoparticles of average diameter between 20 and 200 nm; capable of forming a stable colloidal suspension in a saline medium; at least a portion of which consists of a core and, if appropriate, a matrix coating the core; and, whose core and / or, where appropriate, the matrix, comprise at least one or more fluorescent entities capable of producing at least one memory effect fluorescence signal, that is to say a signal fluorescence irreversibly modified depending on the physico-chemical conditions encountered in the subsoil; the diffused injection liquid is collected at different times after the injection period; and the fluorescent memory effect signal or signals emitted by the nanoparticles as a function of time is detected, the analysis of the detected fluorescent effect signal (s) enabling the inference of information on the physico-chemical conditions of the subsoil. geological study, for example of the oil field. In a preferred embodiment of the process according to the invention, at least a part of the nanoparticles comprises at least one organic fluorophore and at least one organometallic fluorophore, the combination of the two types of fluorophores being chosen so as to the nanoparticle produces at least one memory effect fluorescence signal.

The invention also relates to a tracer fluid that can be used in particular in the process 10 according to the invention, and characterized in that it comprises nanoparticles: - with a mean diameter of between 20 and 200 nm; - capable of forming a stable colloidal suspension in a saline medium; at least part of which consists of a core and, if appropriate, a matrix coating the core; And, whose core and / or, where appropriate, the matrix, comprises at least one organic fluorophore and at least one organometallic fluorophore, the combination of the two types of fluorophores being chosen so that the nanoparticle produces at least one a memory effect fluorescence signal, said signal being detectable by time resolved fluorescence. In a specific embodiment, the nanoparticles are capable of emitting at least one memory effect fluorescence signal, and at least one stable fluorescence signal, that is to say which does not vary according to the physicochemical conditions. -chemicals encountered or whose variation is not irreversible. DETAILED DESCRIPTION OF THE INVENTION

Method of studying a geological subsoil The studied subsoil (e.g., rocks) may be of varied geological nature. Preferably, it is a question of studying a hydrocarbon underground deposit, and more particularly a petroleum deposit. In particular, it involves measuring the proportion of oil and water around a well as well as characterizing the physicochemical properties such as pH or redox potential.

Nanoparticles: The injection fluids used in the process according to the invention comprise nanoparticles with the following characteristics: they have a mean diameter of between 20 and 200 nm; They are capable of forming a stable colloidal suspension in a saline medium; they have at least one part consisting of a core and, if appropriate, a matrix coating the core; the core and / or, where appropriate, the matrix, comprise at least one or more fluorescent entities capable of producing at least one memory effect fluorescence signal, that is to say a modified fluorescence signal irreversibly depending on the physico-chemical conditions encountered in the subsoil.

These nanoparticles are detectable, that is to say that one can identify their presence or not in the medium beyond a certain concentration and that one can even quantify their concentration as soon as they are present in the middle.

These nanoparticles are capable of forming a stable colloidal suspension in a saline medium, which sediments little. For example, this suspension shows no precipitation or agglomeration over time, e.g. after 6 months at room temperature.

According to an advantageous modality of this process, the core of the nanoparticles contains at least one material chosen from the group comprising: semiconductors, noble metals (eg Au, Ag, Pt), fluorides, vanadates or oxides of rare earths and their mixtures and / or alloys; preferably a lanthanide; their alloys and mixtures thereof and, more preferably still, a lanthanide chosen from the subgroup consisting of: Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm and Yb, and their mixtures and / or alloys .

If desired, the nanoparticles furthermore contain a preferably transparent matrix chosen from the group of materials comprising: silicas, polysiloxanes, aluminas, zirconiums, aluminates, aluminophosphates, metal oxides (for example TiO 2, ZnO, CeO 2, Fe 2 O 3, ...) and their mixtures and / or alloys, this matrix including within it and / or on its surface: i. luminescent entities selected from the group consisting of: rare earth semiconductors, oxides, fluorides or vanadates, organic fluorescent molecules (preferably fluorescein and / or rhodamine), transition metal ions, rare earth ions bound or not to complexing molecules and / or to molecules for improving their absorption and their mixtures and / or alloys, u. optionally other entities allowing a modification of the luminescence properties and chosen from the group comprising: noble metal particles and their mixtures and / or alloys; iii. and the mixtures of these entities (i) and (ii).

The nanoparticles preferably have a matrix functionalized on the surface, that is to say which comprises R radicals grafted, preferably covalently, preferably based on 5 Si-R silane bonds at the surface and derived from: i. optionally hydrophilic compounds, preferably hydrophilic organic compounds, with molar masses of less than 5000 g / mol and more preferably less than 450 g / mol, preferably chosen from organic compounds comprising at least one of the following functions: : alcohol, carboxylic acid, amine, amide, ester, ether-oxide, sulfonate, phosphonate and phosphinate, and mixtures of these hydrophilic compounds optionally charged, neutral hydrophilic compounds, preferably a polyalkylene glycol, more preferably a polyethylene glycol, diethylenetriamine pentaacetic acid (DTPA), dithiolated DTPA (DTDTPA) or a succinic acid, and mixtures of these neutral hydrophilic compounds, one or more compounds, preferably hydrophobic polymers; iv. or their mixtures.

The matrix may comprise, where appropriate, other materials selected from the group consisting of silicas, aluminas, zirconiums, aluminates, aluminophosphates, metal oxides, or metals (example: Fe, Cu, Ni, Co ...) passivated on the surface by a layer of the oxidized metal or another oxide and their mixtures and alloys.

In a particular embodiment, said nanoparticles comprise: a core consisting of a noble metal or an alloy of noble metals, a matrix comprising (i) polysiloxanes, (ii) an organic fluorophore, and (iii) ) an organometallic fluorophore, said fluorophores being covalently bound to the polysiloxanes, said matrix being functionalized on its surface to form silane bonds Si-R, said radicals -R being constituted for at least 50%, preferably at least 75% neutral or charged hydrophilic compounds, preferably from polyethers or polyols, or mixtures thereof.

Advantageously, the matrix of the nanoparticles comprises -R radicals grafted at least one R radical for 10 nm 2 of surface and preferably at least one for 1 nm 2. In order to control the interactions between, on the one hand, the solid medium to be studied, namely for example the geological subsoil (eg rocks) containing the oil reservoir and, on the other hand, the nanoparticles, it is possible according to an advantageous arrangement of the invention to adjust the hydrophilic lipophilic balance and / or the zeta potential of the matrix of the nanoparticles as a function of the subsoil to be studied.

To do this, for example, either the same surface charge is expected for the nanoparticles and rocks of the solid medium, in order to create a repulsion and limit the interactions, or the respective charges are modulated so that the nanoparticles and the rocks of the medium solid interact in a controlled manner and / or specific to certain rocks.

The nanoparticles according to the invention have an average diameter of preferably between 20 nm and 100 nm, for example between 20 nm and 50 nm. In an advantageous embodiment, the nanoparticles according to the invention have a polydispersity index of less than 0.3, preferably less than 0.2, for example less than 0.1.

The size distribution of the nanoparticles is for example measured using a commercial particle size analyzer, such as a PCS-based Malvern Zeta sizer Nano-S granulator (Photon Correlation Spectroscopy). This distribution is characterized by a mean diameter and a polydispersity index.

For the purposes of the invention, "mean diameter" means the harmonic mean of the diameters of the particles. The polydispersity index refers to the width of the size distribution derived from the cumulant analysis according to ISO 13321: 1996.

An essential characteristic of the study method according to the invention lies in the use of nanoparticles capable of producing a memory effect signal.

Within the meaning of the invention, we speak of a fluorescent signal with a memory effect, a signal whose characteristics, for example the fluorescence intensity of the emission spectrum, the excitation spectrum, the transmission lifetime, or the quantum yields are irreversibly modified according to certain physico-chemical conditions encountered in the subsoil traversed. Thus, the nature and / or the intensity of the alteration of the fluorescent signal makes it possible to deduce certain physico-chemical conditions from the environment traversed.

The physicochemical conditions studied include, for example, the temperature of the subsoil, the pH, the hydrocarbon content or the redox potential of the subsoil traversed.

In an advantageous embodiment, use will be made of nanoparticles comprising at least one or more fluorescent entities making it possible to produce at least one memory effect fluorescence signal and one or more fluorescent entities producing a stable signal, that is to say, unlike the memory effect, a signal that is not irreversibly modified depending on the physicochemical conditions encountered. By way of examples of fluorescent entities producing a stable signal, mention may be made of lanthanides or other entities whose luminescence is not sensitive to the local environment because the f orbitals involved are not widely available for interact with the elements present in their sphere of coordination and thus modify their luminescence properties.

In a preferred embodiment of the invention, at least a portion of the nanoparticles comprises: i. at least one organic fluorophore, and, at least one organometallic fluorophore, the combination of the two types of fluorophores being chosen so that the nanoparticle produces at least one memory effect fluorescence signal.

It is known that the fluorescence signal of certain organic fluorophores is irreversibly modified according to the physicochemical conditions encountered by the tracer carrying fluorophores, and in particular as a function of the pH, the temperature, and / or the redox potential. .

By way of example of an organic fluorophore that can be used, in combination with an organometallic fluorophore, to obtain a fluorescent signal with a memory effect, mention may be made of fluorescein (for example fluorescein isothiocyanate FITC), rhodamine 30 (for example Rhodamine). B isothiocyanate RBITC) or other fluorescent species that have emission spectra in the same area as fluorescein or rhodamine, for example products with the trade names Alexa Fluor, Cy Dyes, Atto, F1uoProbes.

Preferably, the organometallic fluorophores of the nanoparticles are chosen from vanadates or rare earth oxides, or mixtures thereof. In a specific embodiment, they are chosen from lanthanides, their alloys and their mixtures, linked to complexing molecules.

In a preferred embodiment, the organometallic fluorophores are detectable by time-resolved fluorescence. Lanthanides linked to complexing molecules are then particularly preferred.

The metals of the lanthanide series include atomic number elements from 57 (lanthanum) to 71 (lutetium). For example, lanthanides will be selected from the group consisting of: Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm and Yb and mixtures and / or alloys thereof, linked to complexing molecules, and preferably europium and terbium.

By "complexing molecules" or "chelating agent" is meant any molecule capable of forming with a metal agent, a complex comprising at least two coordination bonds.

In a preferred embodiment, a complexing agent having a coordination of at least 6, for example at least 8, and a dissociation constant of the complex, pKd, greater than 10 and preferably greater than 15, will be chosen with a lanthanide.

Within the meaning of the invention, the dissociation constant pKd is understood to mean the measurement of the equilibrium between the ions in the complexed state by the ligands and those free dissolved in the solvent. Precisely, it is less the logarithm in the base of the dissociation product (-log (Kd)), defined as the equilibrium constant of the reaction which translates the transition from the complexed state to the ionic state.

Such complexing agents are preferably polydentate chelating molecules selected from families of polyamine-type polycarboxylic acid molecules and having a high potential coordination site number, preferably greater than 6, such as certain macrocycles.

In a more preferred embodiment, DOTA, or 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid, of the following formula or one of its derivatives will be selected.

By "cyclic agent" is meant an organic molecule, comprising at least one aromatic ring or heterocycle, preferably selected from benzene, pyridine or their derivatives, and capable of amplifying the fluorescent signal emitted by the organometallic fluorophore and / or the organic fluorophore, for example a complexing agent bound to lanthanide. These cyclic agents, interesting if they are characterized by a high absorbance, are used in particular to amplify the fluorescent signal emitted by the fluorophores (antenna effect by transfer of the excitation of the agent towards the fluorophore).

The cyclic agent may be grafted covalently either directly to the polysiloxanes of the matrix or to the organometallic and / or organic fluorophore.

In a specific embodiment, the organometallic fluorophores consisting of a lanthanide with a complexing agent are grafted to the polysiloxanes of the matrix of the nanoparticles covalently via an amide function.

Organic fluorophore and organometallic fluorophore contained in the same nanoparticle are chosen so as to produce a fluorescence signal with a memory effect, preferably detectable by fluorescence in time resolved.

In a more particularly preferred embodiment, the nanoparticles comprise at least one organic fluorophore chosen from fluorescein or one of its derivatives and at least one organometallic fluorophore chosen from europium (Eu) or terbium (Tb), linked to a complexing agent.

In another preferred embodiment, the nanoparticles comprise at least one organic fluorophore chosen from rhodamine or one of its derivatives, and at least one organometallic fluorophore selected from Eu or Tb, linked to a complexing agent.

In order to multiply the information on the environment under study, the injection liquid may comprise a mixture of nanoparticles, each type of nanoparticle being characterized by the emission of one or more specific fluorescence signals, and in that said signals emitted by each type of nanoparticles are detectable by multiplex detection means. The multiplex detection makes it possible to analyze several fluorescence signals (characterized for example by different wavelengths) in parallel on the same sample. Also, fluorescent entities of different emission and / or excitation wavelengths will be used according to each type of nanoparticle. Other signals emitted by the nanoparticles can also be detected in parallel, and for example signals detectable by chemical analysis, by ICP and / or by magnetic analysis (magnetic transition temperature, for example of Curie or Néel).

In order to further increase the level of information that can be collected, the injection liquid comprises at least two types of nanoparticles which are distinguished by their hydrophilic / lipophilic balance and / or their zeta potential, so that part of the nanoparticles has a fluorescent signal delayed compared to the other part of the nanoparticles because of their interaction with the subsoil. Thus, for example, nanoparticles interacting with certain rocks of the subsoil will have their memory effect signal more strongly modulated relative to the nanoparticles interacting little or not at all with these same rocks.

Nanoparticles useful in the process of the invention and their preparation are shown in the Examples below.

Methodology

In a preferred application of the process according to the invention, the injection liquid is injected and collected in the same well (the injection well and the production well are identical) by inversion of the flow of the injected liquid.

According to a remarkable modality of the process according to the invention, prior to the analysis of the diffused liquid, this is concentrated, preferably by filtration or dialysis, and more preferably still, by tangential filtration and preferably by use of Threshold membrane of cuts below 300 kDa

The amount of tracer in the diffused liquid can be measured by fluorescence detection and / or by chemical analysis and / or by ICP and / or by magnetic analysis (magnetic transition temperature, eg Curie or Neel).

According to a variant for measuring the amount of tracer in the diffused liquid, at least one fluorescence detection is carried out in time resolved, that is to say 5 triggered the detection with delay (eg a few microseconds) after an impulse excitation of one or more fluorescent entities contained in the nanoparticle and likely to emit a "stable" signal, that is to say that has not been irreversibly modulated according to the physicochemical conditions encountered.

The fluorescent signal (s) with memory effect is measured, preferably as a function of the time following the injection, again, preferably by time resolved fluorescence. By comparing the signal or signals obtained as a function of time with respect to a stable signal, the modifications induced by the physicochemical conditions encountered during the diffusion of the injection liquid in the vicinity of the well are deduced therefrom.

In a particular embodiment, the method of the invention makes it possible to obtain information on the temperature variations experienced by the tracer fluid in the subsoil traversed. In another particular embodiment, the pH variations are deduced in the subsoil traversed. In another particular embodiment, the rate of exposure to certain hydrocarbons is deduced therefrom.

In ection liquid ... (waters) .. po!: .. the study. of a solid, solid medium, to see. . For example, according to another of its objects, the invention relates to an injection liquid (or tracer fluid) in a petroleum reservoir that can be used in particular in the process defined above, characterized in that it comprises nanoparticles: of average diameter between 20 and 200 nm; - capable of forming a stable colloidal suspension in a saline medium; at least part of which consists of a core and, if appropriate, a matrix coating the core; and, whose core and / or, where appropriate, the matrix, comprises at least one organic fluorophore and at least one organometallic fluorophore, the combination of the two types of fluorophores being chosen so that the nanoparticle produces at least one memory effect fluorescence signal, said signal being detectable by time resolved fluorescence.

Advantageously, this liquid comprises water and nanoparticles (or mixture of nanoparticles) as defined above.

Use of nanoparticles

According to another of its objects, the invention relates to a new use of the nanoparticles as defined above as tracers in injection waters of a petroleum deposit intended for the study of said deposit by diffusion of these injection waters. through this deposit, in particular to evaluate the volumes of oil in reserve in the deposit.

According to another application, for example in exploration or prospecting methods including hydraulic fracturing, it is possible to map the temperature history of the nanoparticles after diffusion in the vicinity of an injection well and then to deduce the presence of a or several fracturing lines.

EXAMPLES. DESCRIPTION OF THE FIGURES FIG. 1 shows the emission spectra of the three solutions according to Preparation 1, brought to room temperature with the excitation wavelength 330 nm (FIG La) and 395 nm (FIG. 0.1 ms delay and 5 ms acquisition time - FIG. 2 shows the emission spectrum of the three solutions according to Preparation 3 brought back to ambient temperature with excitation wavelength 285 nm (delay 0.1 ms, time 5ms acquisition). FIG. 3 shows the emission spectrum of the two solutions according to preparation 2 brought back to ambient temperature with excitation wavelength 330 nm (delay 0.1 ms, acquisition time 5 ms). FIG. 4 shows the emission spectrum of the three solutions according to Preparation 4 brought back to ambient temperature with excitation wavelength 285 nm (delay 0.1 ms, acquisition time 5 ms).

FIG. 5 shows the excitation spectrum at a fixed emission for europium at 615 nm of the three solutions according to Preparation 1 at different pH (0.1 ms delay, 5 ms acquisition time). FIG. 6 shows the excitation spectrum at a fixed emission for europium at 615 nm of the two nanoparticle solutions according to Preparation 1 in the DEG and a DEG / water mixture (delay 0.1 ms, time of 5 ms acquisition). FIG. 7 shows the excitation spectrum of the three colloid solutions prepared according to Preparation 1, brought to room temperature with the emission wavelength of 615 nm, 0.1 ms delay, 5 ms acquisition time. Preparation 1. Colloidal solution of nanoparticles with a gold core and a silica matrix encapsulating fluorescein-derived organic fluorophores and europium (DTPA) complexes.

In a 10 mL bottle, 200 mg of diethylenetriaminepentaaceticbisanhydride (DTPABA), 0.130 mL of APTES and 0.065 mL of triethylamine are added with 4 mL of DMSO (dimethylsulfoxide) with vigorous stirring. After 24 hours, 200 mg of EuC13,6H20 is added and the mixture is stirred for 48 hours. In a 2.5 mL bottle, 20 mg of FITC (fluorescein isothiocyanate) are introduced with 0.5 mL of APTES ( 3-aminopropyl) triethoxysilane) with vigorous stirring. It is homogenized at room temperature for 30 minutes. In a 500 mL flask, 36 mL of Triton X-100 (surfactant), 36 mL of n-hexanol (co-surfactant), 150 mL of cyclohexane (oil) and 21 mL of aqueous solution containing 9 mL of HAuC14. 3H2O at 16.7 mM, 9 mL of 32.8 mM MES (Sodium 2-mercaptoethanesulfonate) and 3 mL of 412 mM NaBH4 are introduced with vigorous stirring. After 5 minutes, 0.400 mL of fluorescein-containing solution is added to the microemulsion with 1 mL of the solution containing the europium complex. Then, 0.200 mL of APTES and 1.5 mL of TEOS (tetraethylorthosilicate) are also added to the microemulsion. The polymerization reaction of the silica is completed by the addition of 0.800 ml of NH 4 OH after 10 minutes. The microemulsion is allowed to stir for 24 hours at room temperature. Then, 190 μl of 50% Silane-gluconamide (N- (3-Triethoxysilylpropyl) gluconamide) in ethanol is added to the microemulsion with stirring at room temperature.

After 24 hours, 190 μL of silane-gluconamide is again added to the solution, still stirring at room temperature.

After 24 hours, the microemulsion is destabilized in a separatory funnel by adding a mixture of 250 ml of distilled water and 250 ml of isopropanol. The solution is allowed to settle at least 15 minutes and the lower phase containing the particles is recovered.

The colloidal solution recovered is then placed in a 300 kDa VIVASPIN® tangential filtration system and centrifuged at 4000 rpm until a purification rate of greater than 500 is obtained.

The solution thus obtained is then filtered at 0.2 μm and diluted by 5 in DEG (diethylene glycol). The solution obtained is composed of particles of average size 50.25 nm and polydispersity index 0.091 with very good colloidal stability in a salty aqueous medium (up to 100 g of salts / L).

Preparation 2: Colloidal solution of nanoparticles with a gold core and a silica matrix encapsulating organic fluorophores derived from rhodamine B and complexes (DTPA) of europium.

The synthesis is similar to that described for Preparation 1 with the difference that the 20 mg of fluorescein isothiocyanate is replaced by 20 mg of rhodamine B isothiocyanate (RBITC). The rest of the synthesis is identical. The solution thus obtained is composed of particles having a mean size of 48 nm and a polydispersity index of 0.072.

Preparation 3: Colloidal solution of nanoparticles with a gold core and a silica matrix encapsulating organic fluorophores derived from fluorescein and complexes (DTPA) of terbium.

The synthesis is similar to that described for Preparation 1 except that the 200 mg of EuC13,6H20 is replaced by 200 mg of TbC13,6Hz0. The rest of the synthesis is identical. The solution thus obtained is composed of particles of average size 43 nm and polydispersity index 0.069. Preparation 4: Colloidal solution of nanoparticles with a gold core and a silica matrix encapsulating organic fluorophores derived from rhodamine B and complexes (DTPA) of terbium.

The synthesis is similar to that described for Preparation 1 with the difference that the 20 mg of fluorescein isothiocyanate is replaced by 20 mg of rhodamine B isothiocyanate (RBITC) and that the 200 mg of EuC13,6H20 are replaced by 200 mg of TbC13 , 6Hz0. The rest of the synthesis is identical. The solution thus obtained is composed of particles of average size 46 nm and polydispersity index 0.073.

Results

Example 1: Detection of a memory effect fluorescent signal as a function of environmental temperature using nanoparticles according to Preparation 1

Three samples of 10 ml of colloidal solutions of nanoparticles obtained according to Preparation 1 are heated at 80 ° C. respectively for 0, 1 and 72 hours. The fluorescence study is then carried out and indicates a strong variation of the emission spectra especially those in time resolved. Figure 1 shows the emission spectrum of the three solutions brought back to room temperature with excitation wavelength 330 nm (Fig. La), and 395 nm (Fig. Lb). The luminescence curves (Fig. La) show a clear increase in the emission intensity of the particles (peak at 615 nm, specific for europium) in relation to the heat treatment time at 80 ° C. when the excitation 25 is performed at 330 nm, whereas at 395 nm no variation is observed (Fig. Lb). The ratio of the emission peaks between these different excitations can thus serve as probes to measure the exposure time of the particles at the temperature 80 ° C. Example 2: Detection of a memory effect fluorescent signal as a function of environmental temperature using nanoparticles according to Preparation 3

Three samples of 10 ml of colloidal solutions of nanoparticles obtained according to Preparation 3 are heated at 80 ° C. respectively 0, 1 and 72 h. The fluorescence study is then carried out and indicates a strong variation of the emission spectra especially those in time resolved. Figure 2 shows the emission spectrum of the three solutions brought to room temperature with excitation wavelength 285 nm.

The luminescence curves show a clear increase in the emission intensity of the particles (peak at 550 nm, specific for terbium) in relation to the heat treatment time at 80 ° C. The intensity of the emission peaks can therefore be used as probes to measure the exposure time of the particles at 80 ° C, with an increase in intensity as a function of the exposure time.

Example 3: Detection of a fluorescent signal with memory effect as a function of the temperature of the environment using nanoparticles according to Preparation 2

Two samples of 10 ml of colloidal solutions of nanoparticles obtained according to Preparation 2 are heated at 80 ° C. respectively 0 and 1 h. The fluorescence study is then carried out and indicates a strong variation of the emission spectra especially those in time resolved. FIG. 3 shows the emission spectrum of the two solutions brought back to ambient temperature with 330 nm excitation wavelength.

The luminescence curves show a clear decrease in the emission intensity of the particles (peak at 550 nm, specific for terbium) in relation to the heat treatment time at 80 ° C. The intensity of the emission peaks can therefore be used as probes to measure the exposure time of the particles at the temperature 80 ° C, with a decrease in the intensity as a function of the exposure time.

Example 4: Detection of a fluorescent signal with memory effect as a function of the temperature of the environment using nanoparticles according to Preparation 4

Three samples of 10 ml of colloidal solutions of nanoparticles obtained according to Preparation 4 are heated at 80 ° C. respectively 0, 1 and 72 h. The fluorescence study is then carried out and indicates a strong variation of the emission spectra especially those in time resolved. Figure 4 shows the emission spectrum of the three solutions brought to room temperature with excitation wavelength 285 nm.

The luminescence curves show a clear decrease in the emission intensity of the particles (peak at 550 nm, specific for terbium) in relation to the heat treatment time at 80 ° C. The intensity of the emission peaks can therefore be used as probes to measure the exposure time of the particles at the temperature 80 ° C, with a decrease in the intensity as a function of the exposure time.

EXAMPLE 5 Detection of a Fluorescent Signal with Memory Effect as a Function of the pH of the Environment Using Nanoparticles According to Preparation 1 Three samples of 1 ml of colloidal solutions of nanoparticles are obtained according to Preparation 1 and dispersed in 10 ml of solution aqueous solution brought back by a sodium hydroxide / hydrochloric acid mixture at a pH of respectively 1, 5 and 12. The fluorescence study is then carried out and indicates a strong variation of the emission spectra, in particular those in time resolved. Figure 5 shows the excitation spectrum at a fixed emission for europium at 615 nm of the three solutions at these different ambient pH.

The luminescence curves show a clear increase in the excitation spectrum of the particles in relation to the increase in pH. The intensity of the emission peaks (or excitation) can therefore be used as probes to measure the exposure pH of the particles. Example 6 Detection of a Fluorescent Signal with a Memory Effect as a Function of the Nature of the Environment Fluid Using Nanoparticles According to Preparation 1

Two 5 mL samples of colloidal nanoparticle solutions were obtained according to Preparation 1 and dispersed in 5 mL of water and 5 mL of DEG, respectively. Both solutions are then heated at 80 ° C for 3 days. The fluorescence study is then carried out and indicates a strong variation of the excitation spectra, in particular those in time resolved. Figure 6 shows the excitation spectrum at a fixed emission for europium at 615 nm of both solutions. The luminescence curves show a clear degradation of the excitation spectrum of the particles in relation to the increasing water content. The intensity of emission peaks (or excitation) can thus serve as probes for measuring the exposure rate of particles at different water contents.

Example 7: Detection of a memory effect fluorescent signal as a function of temperature variations of the environment using nanoparticles according to Preparation 1

Three samples of 1 ml of colloidal solutions of nanoparticles obtained according to Preparation 1 are mixed with 9 ml of water are heated for 1 hour at 60, 80 and 100 ° C. respectively. The fluorescence study is then carried out and indicates a strong variation of the excitation spectra, in particular those in time resolved. FIG. 7 shows the excitation spectrum of the three solutions brought back to ambient temperature with the emission wavelength of 615 nm.

The luminescence curves show a clear variation in the excitation intensity of the 330 nm component of the particles in relation to the temperature of the treatment. The intensity of the excitation peaks can therefore serve as probes for measuring the exposure temperature of the particles, with a decrease in the intensity as a function of the exposure temperature.

Claims (4)

REVENDICATIONS1. A method of studying a geological subsoil, such as a petroleum deposit, by diffusion of an injection liquid into said subsoil, characterized in that it comprises the following steps: - injection, in the subsoil to be studied, an injection liquid comprising nanoparticles: o of mean diameter between 20 and 200 nm; Able to form a stable colloidal suspension in a saline medium; at least a portion of which consists of a core and, if appropriate, a matrix coating the core; and, whose core and / or, where appropriate, the matrix, comprise at least one or more fluorescent entities capable of producing at least one memory effect fluorescence signal, that is to say a fluorescence signal. modified according to the physicochemical conditions encountered in the subsoil; the diffused injection liquid is collected at different times following the injection period; And the fluorescent effect signal (s) emitted by the nanoparticles as a function of time is detected, the analysis of the detected fluorescent effect signal (s) making it possible to deduce therefrom information on the physico-chemical conditions of the sub-component. geological soil studied, for example oil field. 25 2. Method according to claim 1, characterized in that the injection liquid is collected by the injection well by inverting the flow of the fluid after injection and diffusion. 30 3. Method according to one of claims 1 or 2, characterized in that at least a portion of the nanoparticles comprises i. at least one organic fluorophore, and, ii. at least one organometallic fluorophore, the combination of the two types of fluorophores being chosen so that the nanoparticle produces at least one memory effect fluorescence signal. 5. 6. 7. 25 30 8. 35 4. Method according to claim 3, characterized in that the organometallic fluorophore is chosen from rare earth ions bound to a complexing agent, preferably from lanthanides linked to a complexing agent. Process according to any one of Claims 1 to 4, characterized in that the said injection liquid comprises a mixture of nanoparticles, each type of nanoparticle being characterized by the emission of one or more specific fluorescent signals, and in that said signals emitted by each type of nanoparticle are detectable by multiplex detection means. Process according to any one of Claims 1 to 5, characterized in that the fluorescent signal (s) with a memory effect are detected by fluorescence in time resolved. Process according to any one of Claims 1 to 6, characterized in that the nanoparticle matrix comprises covalently grafted R radicals based on silane Si-R bonds at the surface and derived from: i. charged hydrophilic compounds, preferably hydrophilic organic compounds of molar masses less than 5000 g / mol and more preferably less than 450 g / mol, preferably chosen from organic compounds containing at least one of the following functions: alcohol carboxylic acid, amine, amide, ester, ether-oxide, sulfonate, phosphonate and phosphinate, and mixtures of these charged hydrophilic compounds, neutral hydrophilic compounds, preferably a polyalkylene glycol, more preferably still a polyethylene glycol, diethylenetriamine-pentaacetic acid (DTPA), dithiolated DTPA (DTDTPA) or a succinic acid, and mixtures of these neutral hydrophilic compounds, iii. one or more hydrophobic compounds; iv. or their mixtures. Process according to any one of Claims 1 to 7, characterized in that the injection liquid comprises at least two types of nanoparticles which are distinguished by their hydrophilic / lipophilic balance and / or their zeta potential, so that part of the nanoparticles has a delayed fluorescent signal compared to the other part of the nanoparticles due to their interaction with the subsoil. Process according to Claim 8, characterized in that at least a part of the nanoparticles has a hydrophilic / lipophilic balance and / or the zeta potential adjusted so as not to interact with the subsoil medium in which they diffuse and at least another part of the nanoparticles has a hydrophilic / lipophilic balance and / or a zeta potential adjusted to interact with specific subsoil rocks. 10. tracer fluid used in particular in the process according to any one of claims 1 to 9, characterized in that it comprises nanoparticles: - average diameter between 20 and 200 nm; - capable of forming a stable colloidal suspension in a saline medium; at least part of which consists of a core and, if appropriate, a matrix coating the core; and, whose core and / or, where appropriate, the matrix, comprises at least one organic fluorophore and at least one organometallic fluorophore, the combination of the two types of fluorophores being chosen so that the nanoparticle produces at least one memory effect fluorescence signal, said signal being detectable by time resolved fluorescence. 11. tracer fluid according to claim 10, characterized in that said organometallic fluorophore is selected from rare earth ions bound to a complexing agent. Tracer fluid according to claim 11, characterized in that the rare earth ions are chosen from the group of lanthanides consisting of Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm and Yb and mixtures thereof. / or alloys. 13. Tracer fluid according to any one of claims 10 to 12, characterized in that at least a portion of the nanoparticles comprises at least one organic fluorophore selected from fluorescein and at least one organometallic fluorophore comprising a lanthanide selected from europium or terbium, said lanthanide being bound to a complexing agent. 14. tracer fluid according to any one of claims 10 to 12, characterized in that at least a portion of the nanoparticles comprises at least one organic fluorophore selected from rhodamine or one of its derivatives and at least one organometallic fluorophore selected from l europium or terbium bound to a complexing agent. 15. tracer fluid according to any one of claims 10 to 14, characterized in that the complexing agent is selected from the group consisting of DTPA, DOTA and their derivatives. 16. Use of a tracer fluid according to any one of claims 10 to 15, in the study of a hydrocarbon deposit, for example a petroleum deposit. 17. Use of a tracer fluid according to any one of claims 10 to 15, in a method of exploration or prospection of a hydrocarbon reservoir comprising a hydraulic fracturing step, for the mapping of fracture lines.